This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A056471 #11 Aug 22 2017 20:53:12 %S A056471 1,1,2,2,5,5,15,15,52,52,203,203,876,876,4111,4111,20648,20648,109299, %T A056471 109299,601492,601492,3403127,3403127,19628064,19628064,114700315, %U A056471 114700315,676207628,676207628,4010090463 %N A056471 Number of palindromic structures using a maximum of six different symbols. %C A056471 Permuting the symbols will not change the structure. %D A056471 M. R. Nester (1999). Mathematical investigations of some plant interaction designs. PhD Thesis. University of Queensland, Brisbane, Australia. [See A056391 for pdf file of Chap. 2] %H A056471 <a href="/index/Rec">Index entries for linear recurrences with constant coefficients</a>, signature (1,15,-15,-80,80,180,-180,-144,144). %F A056471 Sum stirling2( [(n+1)/2], k) for k from 1 to 6. %F A056471 G.f.: -x*(91*x^8-135*x^6+68*x^4-14*x^2+1) / ((x-1)*(2*x-1)*(2*x+1)*(2*x^2-1)*(3*x^2-1)*(6*x^2-1)). [_Colin Barker_, Dec 05 2012] %Y A056471 Cf. A056452. %K A056471 nonn,easy %O A056471 1,3 %A A056471 _Marks R. Nester_